The large-scale testing of a variety of diseases for possible association with HL-A will be continued. More specifically the new capacity for examining the haplotype frequencies rather than antigen frequencies alone will be utilized. Each disease will then be investigated for possible linkage to the 150 different haplotypes. Definite association with given haplotypes will provide definitive proof of the existence of disease susceptibility genes. Thus HL-A1-W27 haplotypes may not have AS susceptibility genes, whereas HL-A10-W27 haplotypes often appear to have the AS gene. BIBLIOGRAPHIC REFERENCES: Metzer, A.L., Morris, R.I., Bluestone, R., and Terasaki, P.I.: HL-A-W27 in Psoriatic Arthropathy. Arthritis & Rheum. 18:111-115, 1975. Park, M.S., Terasaki P.I.: Storage of Human Lymphocytes at Room Temperature. Transplantation 18:520-524, 1975.